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TELEPHONE 330313133. No. 305,927. Patented Sept. 30, 18.84.

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UNITED STATES PATENT GEORGE M. HOPKINS, OF BROOKLYN, NEW YORK.

TELEPHONE-RECEIVER.

IEEGIPICATION forming part of Letters Patent No. 305,927, datedSeptember 30, 1884.

Application filed February 29. 1884.

(No model.)

To all whom it may concern:

Be it known that I, GEORGE M. HOPKINS, a citizen of the United States,residing in Brooklyn, in the county of Kings and State of New York, haveinvented a new and useful Improvement in ReccivingTelephones; and I dohereby declare that the following is afull, clear, and exact descriptionthereof, reference being had to the accompanying drawings, forming apart of this specification.

My invention relates to magneto receivingtelephones; audit consists inan arrangement of curved permanent magnets secured to the diaphragm atone end and attached at the other end to a central pole-piece common toall of the magnets, and carrying a helix for receiving the telephoniccurrent.

It further consists in connecting an auxiliary diaphragm with the pole,for the purpose of utilizing the vibrations of'the said polepiece andthecurved magnets.

Figure 1 is asectioual View of my improved telephone-receiver, and Fig'2 is a section taken on line a: w in Fig. 1.

The diaphragm A is clamped on the cell 13 by the apertured cap 0. Threeor more perinanent bar-magnets, D, bent at right angles and then curvedspirally, are secured by their straight ends to the diaphragm A, nearits pcriphery, and their curved ends converge toward the center of thecell B, and are clamped by the washer a and screw b to the enlargedinner end of the pole-piece E, supporting the said pole-piece axially tothe cell, and with the smaller end near but not touching the cen ter ofthe diaphragm. Upon the pole-piece E is mounted a helix, F, whoseterminals-are connected with the wires of the telephonecircuit.

Upon the back of the cell B, opposite the diaphragm A, and parallel withit, is secured an auxiliary diaphragm, G, by means of the cap H, and thecenter of the said diaphragm is secured to the washer c and pole-piece Eends of the bar-magnets to the pole-piece. The diaphragm G partakes, ofthe vibrations of the magnets and pole-piece, and it need not con sistof magnetic material. The cap H has a chamber, 0, which communicateswith the space d between the diaphragm A and cap 0, through the passages6, formed in the caps and in the body of the cell. lVhen changesoccur inthe current traversing the helix F,

the changes effected thereby in the magnetism 5 of the core E cause thealternate attraction and release of the diaphragm A, and a reciprocalattraction of the core, and a corresponding, although diminished, motionof the parts attached to the core, including the diaphragm G. The soundsproduced by the diaphragm G areoommunicated to the car through thechamber 0, passages c, and space (I, and serve to re-enforce the soundproceeding from the diaphragm A.

Having thus described my invention, what- I claim as new, and desire tosecure by Letters Patent, is-

The combination, with a series of converg ing bar-magnets clamped to avibratory polepicce, of an auxiliary diaphragm located in the back ofthe receiver-case, and connected with the vibratory core, the saidauxiliary diaphragm acting in conjunction with the usual diaphragm tore-enforce the sound, as specified.

GEORGE M. HOPKINS. Witnesses:

Oniis. L. Cons, HERMAN G. HAGES.

by the same screw, I), that binds the curved 5

